What Is a Switched PDU vs. a Metered PDU?

Energy costs continue to command the lion’s share of the budget in data centers of all sizes, and those costs climb as power densities increase. Effective power management has become an essential element of day-to-day data center administration.

You can’t manage what you don’t measure, so you must gather data on power usage. Metered power distribution units (PDUs) can aid in that process. IT personnel also need a means of managing the data center infrastructure remotely. Switched PDUs enable remote control of power outlets, reducing operational overhead.

Check out our past blogs for a refresher on what a PDU does, how PDUs work, and the different types of PDUs. In this blog, we’ll explore the differences between metered vs. switched PDUs in detail.

What Is a Metered PDU?

Metered PDUs also provide information about the power being consumed by the PDU as a whole or by individual outlets. Some of the data provided includes:

• Voltage (V)
• Current (A)
• Active Power (kW)
• Apparent Power (kVA)
• Energy (kWh)
• Power Factor (ratio of kW to kVA)

Metered PDUs should provide “billing-grade” accuracy, which means that the data is accurate within +/- 1%. Best-in-class units conform to the ISO / IEC 62053-21 standard for electricity metering equipment.

Metered PDUs come in two basic types: input metered and outlet metered. Which you choose depends on the level of granularity you need. If you only need to monitor the power consumption of an individual cabinet, input metered could be the right choice. However, if you need insight into the power consumption of the cabinet overall and the equipment within, outlet metered could be your best choice.

Input-Metered PDUs

Input-metered PDUs measure the power coming into the PDU. Real-time phase and circuit breaker metering reduces the risk of overloads and facilitates load balancing and capacity planning. This is particularly important in racks with redundant power. If both PDUs are near capacity and one fails, a circuit breaker will likely trip during failover.

Outlet-Metered PDUs

Outlet-metered PDUs measure the power used by each outlet. Metering at the outlet level provides benefits similar to input metering. However, it also allows administrators to better understand power usage at the device level so they can identify underutilized or “zombie” equipment and compare the efficiencies of various units. Outlet-metered PDUs also aid in allocating power costs to specific business units, departments, user groups, or projects.

What Is a Switched PDU?

Switched PDUs enable administrators to control entire PDUs and/or individual power outlets on a PDU through a network interface with a few clicks or keystrokes. That simple capability brings many benefits to the modern data center.

Power Cycling Equipment

In many cases, all that’s required to fix a failed piece of equipment is to turn it off and back on. Traditionally, a technician would have to visit the piece of equipment to perform this simple task, increasing operational costs and extending equipment downtime. Switched PDUs make it possible to power cycle equipment remotely.

Staged Power-Up Sequencing

Administrators can use switched PDUs to power down noncritical devices in an outage or other disruption. When power is restored after an outage, administrators can stage power-up sequencing, allowing the data center to ease back up to full power while avoiding surges. Best-in-class switched PDUs will enable you to control outlets automatically through scripts.

Outlet Lockout

By locking out PDU receptacles that aren’t used, data center managers can enforce ticketing procedures that ensure equipment is installed in racks and cabinets with the right amount of power on the proper phase (single phase vs. 3 phase power). Outlet lockout can also enhance security by preventing the installation of unauthorized equipment.

Power Management

Data center managers can also use switched PDUs to improve power management. Power is often wasted when noncritical equipment continues to run when it’s not being utilized. Switched PDUs enable administrators to manage power on a per-outlet basis to avoid wasting energy.

Metered PDUs vs. Switched PDUs

Metered PDUs and switched PDUs perform two separate functions in the data center. One measures power consumption and delivers those metrics over a network connection, while the other enables remote control over power outlets. Which you choose depends upon the functionality that best meets your power management requirements.

There are also PDUs that combine the two capabilities. For example, Enconnex offers input metered / outlet switched and outlet metered / outlet switched PDUs with hot-swappable network management modules for rapid resolution of problems and easy upgrades. They can be monitored through the embedded web interface or telnet, SNMP, or SSH connections and provide user-programmable startup sequencing for even greater efficiency and control.

Check out our PDU buying guide for more information on how to choose the right PDU for your environment. Additionally, our power experts are always here to help you determine what PDU features you need and select the right products for each application. Let us show you how metered and switched PDUs can help you reduce costs and operational overhead while enabling the remote management of your data center.

We are also getting ready to launch a new line of TAA-compliant, made-in-America basic PDUs. View our catalog to see all our PDUs for sale, and contact us to get the right PDU for your use case and to stay up to date on our latest offerings.